Requires NAD+, which dehydrogenates the -CHOH- group to -CO- at C-5 of the glucose 6-phosphate, making C-6 into an active methylene, able to condense with the -CHO at C-1. Finally, the enzyme-bound NADH reconverts C-5 into the -CHOH- form.

Rate-limiting Description

"CONCLUSIONS: The rate-limiting step of inositol biosynthesis, catalyzed by MIP synthase, is inhibited by VPA; inositol depletion is a first event shown to be common to lithium and VPA." (15576064)